Some species of ants have a mutually beneficial relationship (mutualism) with aphids in order to "milk" the aphids for honeydew, a sweet substance secreted by the aphids and prized as food by the ants.

Important natural enemies of aphids include the predatory ladybirds/ladybugs/ladybeetles (Coleoptera: Coccinellidae), hoverfly larvae (Diptera: Syrphidae), and lacewings (Neuroptera: Chrysopidae), and entomopathogenic fungi like Lecanicillium lecanii and the Entomophthorales.